Conventionally, in facilities such as factories, hospitals or grocery stores, there has been a need for removing dust or dirt adhering to persons entering into or vehicles carried into the facilities. Further, there has recently been a need for removing dust or dirt adhering to person's shoes or cart's wheels not only in facilities such as factories but also in common buildings or rather common houses, because computers or electronic devices, which are negatively affected by dust, have become popular.
In order to satisfy the aforementioned need, Japanese Laid-Open Patent Publication No. 8-322782, for example, discloses a dust removal mat in which dust is removed by applying a suction force of a dust collector or an electric vacuum cleaner.
Such a dust removal mat is provided with a wiping surface, which includes multiple slits, for wiping dust or dirt out of pedestrian's shoe soles. Also, air passages defined with multiple supporting columns are formed below the wiping surface. When a pedestrian applies his or her weight onto the wiping surface, the slits are resiliently deformed and opened so as to serve as suction openings. Thus, dust or dirt adhering to the shoe soles is drawn through the suction openings, and then collected by the dust collector or the electric vacuum cleaner through the air passages below the wiping surface.
Japanese Laid-Open Patent Publication No. 2001-224548 discloses another dust collection system, in which a movable element, which is provided with a brush on its top surface and resiliently biased upward, scratches off dust or dirt on the shoe soles of the pedestrian, while the movable element is, due to the pedestrian's weight, displaced downward so as to define a suction opening, through which the dust or dirt is drawn by a dust collector.
In the aforementioned configuration, air introduced from the suction opening of the dust collection system takes a flow path, which passes through the vicinity of plurally-provided supporting columns or movable elements and then reaches the dust collector.
Accordingly, the air flowing along the flow path is subjected to fluid resistance imposed by the multiple supporting columns or movable elements such that the dust collection efficiency of the dust collector is decreased.
Especially, with respect to the dust collection system of Japanese Laid-Open Patent Publication No. 2001-224548, the number of movable elements needs to be increased to ensure that an effective area for dust collection be greater, while the increase in the number of the movable elements causes fluid resistance to be significantly increased within the main body of the dust collection system. Therefore, the number of the movable elements needs to be limited to a certain number in order to ensure a dust collection efficiency for practical use. Further, in order to reduce the fluid resistance caused by the movable elements as much as possible, the two dimensional arrangement of the movable elements needs to be devised such that the fluid resistance applied to gas flow is optimized.
Patent Document 1: Japanese Laid-Open Patent Publication No. 8-322782
Patent Document 2: Japanese Laid-Open Patent Publication No. 2001-224548